Hammond Commodore MIDI Interface: Pedal Mux Board

A couple of the connectors on the "Ease of Play" board mounted on the back panel of the organ carry signals coming from the bass pedals; -12V is on and 0V is off. It was much easier to tap the signals off of here than trying to wire directly to the bass pedal switches under the organ. (The top of the "Ease of Play" board also is a convenient place to mount the Main PIC Board).

The pedal mux board runs the -12V signals through voltage dividers to turn them into -2V signals so they will looks just like signals from the manual mux boards. Then two 2 CD4067 chips multiplex them down to two signals that get sent back to the Main PIC Board.

Here are the schematic and board layout of the pedal mux board.

Here is what the finished board looks like.